1. Field of the Invention
The present invention relates to a buckle of an insert type comprising female and male members, that is, a buckle main body and an insertion body, and particularly to a buckle for fastening a belt, which is generally used for a clothing, a bag, a helmet, a stroller, a sports equipment or the like.
2. Description of the Prior Art
Conventionally, this kind of buckle is constituted by a buckle main body and an insertion body structured such as that shown in FIG. 11, the buckle main body 101 is formed in a flat cylindrical shape comprising an upper plate 103, a lower plate 104 and side walls 105, is provided with an insertion port 106 in one end, a belt mounting portion 107 on the other end and opening portions 109 in both side surfaces, and is provided with two guide ribs on inner surfaces of the upper plate 103 and the lower plate 104, and the insertion body 102 is provided with a belt mounting portion 107 projected from one end thereof, operation rods 125 projected from both sides of the other end thereof and a guide rod projected from a center thereof. In the buckle structured in the manner mentioned above, an expanding operation portion 129 capable of fitting to the opening portion 109 is provided at a front end of each of the operation rods 125 so as to form an engaging portion, a thin elastic piece is provided from a base portion of the belt mounting portion 107 to the operation portion 129 so as to provide flexibility, a rib is provided in an inner side of the operation portion 129 so as to reinforce, and the guide rod is fitted and inserted between the guide ribs of the upper plate 103 and the lower plate 104. This kind of buckle is disclosed in Japanese Patent Laid-Open Publication No.7-250704.
Further, the insertion type buckle shown in FIG. 12 is constituted by a buckle main body 1' which is structured such that an upper plate 4' and a lower plate 3' are connected by a guide piece provided in a vertical direction at a center thereof, an insertion port 6' and a belt mounting portion are respectively provided at one end and the other end thereof, opening portions 9' continued to the insertion port 6' are formed on both side surfaces, deep recess grooves are provided on inner surfaces of the upper plate 4' and the lower plate 3' along a guide piece from the insertion port 6' and inward hook-shaped portions 10' to be engaged are provided in both sides thereof in a vertical symmetrical manner, and an insertion body 2' which is structured such that a belt mounting portion 7' is provided in one end thereof, flexible insertion leg portions projecting from both sides of a base portion 19' of the belt mounting portion 7' are provided in the other end thereof, a pair of short vertically protruding portions 30' having a great height are projected from a center of the base portion 19' so as to form a groove portion 31' therebetween, operation portions 25' are formed on outer side surfaces of the curved insertion leg portions, the operation portions 25' are continuously formed from the base portion 19' at a substantially equal thickness and outward hook-shaped engaging portions 29' are provided in inner sides of the front ends of the insertion leg portions in a vertically symmetrical manner. In this structure, the insertion leg portion of the insertion body 2' is inserted from the insertion port 6' of the buckle main body 1' so as to engage the engaging portion 29' with the portion 10' to be engaged. This type of buckle is disclosed in Japanese Patent Laid-Open Publication No. 7-289310.
In the buckle shown in FIG. 11, in the case of inserting the insertion body 102 to the buckle main body 101 so as to engage the engaging portion with the portion 110 to be engaged for use, when a strong tensile force is applied between the buckle main body 101 and the insertion body 102, there is a risk that a shearing force is applied between the elastic piece and the operation portion 129 in the operation rod 125 of the insertion body 102 and a crack may generate, and there is also a risk of breaking the thin elastic piece. Further, there is a problem that it is hard to hold the elastic piece of the operation rod 125 against the side walls 105 of the buckle main body 110 in a stable state at a time of engaging.
Further, in the buckle shown in FIG. 12, since the buckle main body 1' does not have means for positively guiding the insertion leg portion at a time of inserting the insertion body 2' into the buckle main body 1' and a pair of projections 30' inserted to the guide piece have a short length, an inserting operation of the insertion body 2' is significantly unstable and troublesome. Still further, since the inner surface of the buckle main body 1' and the insertion body 2' are formed in an inside and outside symmetrical manner, it is possible to insert the insertion body 2' to the buckle main body 1' in an opposite direction, so that there is a problem of a risk that the belt mounted to the insertion body 2' is twisted in place of a normal condition.